WASHINGTON — Declaring “our security is at stake,” President Barack Obama ordered an additional 30,000 U.S. troops into the long war in Afghanistan on Tuesday night, nearly tripling the force he inherited but promising an impatient public to begin withdrawal in 18 months.

The buildup will begin almost immediately — the first Marines will be in place by Christmas — and will cost $30 billion for the first year alone.

In a prime-time speech at the U.S. Military Academy, the president told the nation his new policy was designed to “bring this war to a successful conclusion,” though he made no mention of defeating Taliban insurgents or capturing al-Qaida terrorist leader Osama bin Laden.

“We must deny al-Qaida a safe haven,” Obama said in spelling out U.S. military goals for a war that has dragged on for eight years. “We must reverse the Taliban’s momentum. ... And we must strengthen the capacity of Afghanistan’s security forces and government.”

‘Fastest pace possible’The president said the additional forces would be deployed at “the fastest pace possible so that they can target the insurgency and secure key population centers.”

It marked the second time in his young presidency that Obama has added to the American force in Afghanistan, where the Taliban has recently made significant advances. When he became president last January, there were roughly 34,000 troops on the ground; there now are 71,000.

After the speech, cadets in the audience — some of whom could end up in combat because of Obama’s decision — climbed over chairs to shake hands with their commander in chief and take his picture.

Obama’s announcement drew less-wholehearted support from congressional Democrats. Many of them favor a quick withdrawal, but others have already proposed higher taxes to pay for the fighting.

Republicans reacted warily, as well. Officials said Sen. John McCain, who was Obama’s Republican opponent in last year’s presidential campaign, told Obama at an early evening meeting attended by numerous lawmakers that declaring a timetable for a withdrawal would merely send the Taliban underground until the Americans began to leave.

A war worth fighting?As a candidate, Obama called Afghanistan a war worth fighting, as opposed to Iraq, a conflict he opposed and has since begun easing out of.

A new survey by the Gallup organization, released Tuesday, showed only 35 percent of Americans now approve of Obama’s handling of the war; 55 percent disapprove.

He made no direct reference to public opinion Tuesday night, although he seemed to touch on it when he said, “The American people are understandably focused on rebuilding our economy and putting people to work here at home.”

“After 18 months, our troops will begin to come home,” he said flatly.

In eight years of war, 849 Americans have been killed in Afghanistan, Pakistan and neighboring Uzbekistan, according to the Pentagon.

In addition to beefing up the U.S. presence, Obama has asked NATO allies to commit between 5,000 and 10,000 additional troops. The war has even less support in Europe than in the United States, and the NATO allies and other countries currently have about 40,000 troops on the ground.

He said he was counting on Afghanistan eventually taking over its own security, and he warned, “The days of providing a blank check are over.” He said the United States would support Afghan ministries that combat corruption and “deliver for the people. We expect those who are ineffective or corrupt to be held accountable.”

The speech before an audience of cadets at the military academy ended a three-month review of the war, triggered by a request from the commanding general, Stanley McChrystal, for as many as 40,000 more troops. Without them, he warned, the U.S. risked failure.

The speech was still under way when the general issued a statement from Kabul. “The Afghanistan-Pakistan review led by the president has provided me with a clear military mission and the resources to accomplish our task,” it said. McChrystal is expected to testify before congressional committees in the next several days.

Obama referred to a deteriorating military environment, but said, “Afghanistan is not lost.”

The length of the presidential review drew mild rebukes from normally amiable NATO allies. There was sharper criticism from Republicans led by former Vice President Dick Cheney, who said the president was dithering rather than deciding.

Obama rebutted forcefully.

“Let me be clear: There has never been an option before me that called for troop deployments before 2010, so there has been no delay or denial of resources necessary for the conduct of the war,” he told his audience of more than 4,000 cadets seated in Eisenhower Hall.

New forces will be combat troopsMost of the new forces will be combat troops. Military officials said the Army brigades were most likely to be sent from Fort Drum in New York and Fort Campbell in Kentucky; and Marines primarily from Camp Lejeune in North Carolina.

Key dates in the warOfficials said the additional 30,000 troops included about 5,000 dedicated trainers, underscoring the president’s emphasis on preparing Afghans to take over their own security.

These aides said that by announcing a date for beginning a withdrawal, the president was not setting an end date for the war.

But that was a point on which McCain chose to engage the president at a pre-speech meeting with lawmakers before Obama departed for West Point. “The way that you win wars is to break the enemy’s will, not to announce dates that you are leaving,” McCain said later.

Obama’s address represents the beginning of a sales job to restore support for the war effort among an American public grown increasingly pessimistic about success — and among some fellow Democrats in Congress wary of or even opposed to spending billions more dollars and putting tens of thousands more U.S. soldiers and Marines in harm’s way.

A threat to block fundingSen. Russ Feingold, D-Wis., and liberal House Democrats threatened to try to block funding for the troop increase.

Sen. Carl Levin, the Michigan Democrat who chairs a military oversight panel, said he didn’t think Democrats would yank funding for the troops or try to force Obama’s hand to pull them out faster. But Democrats will be looking for ways to pay for the additional troops, he said, including a tax increase on the wealthy although that hike is already being eyed to pay for health care costs. Another possibility is imposing a small gasoline tax that would be phased out if gas prices go up, he said.

The United States went to war in Afghanistan shortly after the Sept. 11, 2001, al-Qaida terrorist attacks on the United States.

Bin Laden and key members of the terrorist organization were headquartered in Afghanistan at the time, taking advantage of sanctuary afforded by the Taliban government that ran the mountainous and isolated country.

Taliban forces were quickly driven from power, while bin Laden and his top deputies were believed to have fled through towering mountains into neighboring Pakistan. While the al-Qaida leadership appears to be bottled up in Pakistan’s largely ungoverned tribal regions, the U.S. military strategy of targeted missile attacks from unmanned drone aircraft has yet to flush bin Laden and his cohorts from hiding.

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